A box contains only marbles. If ¼ the marbles were removed, the box would be filled to 1/3 of its capacity. If instead 100 marbles were added, the box would be full. How many marbles are there in the box?
ABCD is a parallelogram such that AB is parallel to DC and DA parallel to CB. The length of side AB is 20cm. E is a point between A and B such that the length of AE is 3cm. F is a point between points D and C. Find the length of DF such that the segment EF divide the parallelogram in two regions with equal areas.